Relationship between insulin-like growth factor-1 receptor down-regulation and Kaschin-Beck disease

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Objective To observe the expression level of insulin-like growth factor-1 receptor (IGF-1R) in the cartilage tissue of children with Kaschin-Beck disease (KBD) and T-2 toxin-poisoned rats under low selenium condition, and the effect of IGF-1R inhibitor on apoptosis of human normal chondrocytes (C28/I2 cells), and to investigate the role of IGF-1R in the pathogenesis of KBD. Methods The knuckles of dead children (5 cases) in the KBD areas, car accident death and congenital 6 finger deformity operation children (5 cases) in non-KBD areas in Shaanxi were collected, the expression of IGF-1R in the articular cartilage was detected by immunohistochemistry. Thirty-two male Sprague-Dawley rats with a body mass of 60 - 80 g were selected, according to the body mass, they were divided into the routine feed group (selenium content: 101.5 μg/kg) and the low-selenium feed group (selenium content: 1.1 μg/kg) by random number table method, 16 rats in each group. After 30 days of feeding, the routine feed group was divided into control group and T-2 toxin group (100 ng·kg-1·d-1), the low-selenium feed group was divided into low selenium group and low selenium + T-2 toxin group, 8 rats in each group, the expression of IGF-1R in the articular cartilage of the left knee joint was detected by immunohistochemistry after 30 days of feeding. C28/I2 cells were cultured in vitro and treated with T-2 toxin 0 (control), 6, 12, and 24 μg/L, and each concentration of T-2 toxin was accompanied with sodium selenite (+ 0.1 mg/L) for 72 h. Meanwhile, IGF-1R inhibitor with 0 (control), 250, 500, and 1 000 μg/L was treated on C28/I2 cells for 48 h. The expression levels of IGF-1R mRNA and protein in chondrocytes were detected by Real-time PCR and Western blotting, and the apoptosis of chondrocytes was detected by flow cytometry. Results Compared with the control group [(100.00 ± 0.00)%, (100.00 ± 0.00)%], the expression rates of IGF-1R positive cells in articular cartilage surface and middle layers [(72.71 ± 4.75)%, (36.33 ± 4.32)%] of children in KBD group were significantly reduced (t = 12.852, 32.650, P < 0.01). Compared with control group [(100.00 ± 0.00)%, (100.00 ± 0.00)%, (100.00 ± 0.00)%], the expression rates of IGF-1R positive cells in articular cartilage middle layer [(20.83 ± 2.69)%, (26.45 ± 2.84)%, (20.34 ± 1.82)%], deep layer [(33.55 ± 5.66)%, (48.89 ± 8.39)%, (25.51 ± 7.50)%], and the expression rates of IGF-1R positive cells [(47.50 ± 1.47)%, (28.66 ± 3.58)%, (40.52 ± 6.78)%] in the hypertrophic layer of the metaphyseal plate of rats in low selenium, T-2 toxin, and low selenium + T-2 toxin groups were significantly reduced (P < 0.01). C28/I2 cells were cultured in vitro, compared with the control group, IGF-1R mRNA and protein expression levels in each T-2 toxin groups were significantly reduced (P < 0.05). The expression levels of IGF-1R mRNA (1.95 ± 0.35, 2.44 ± 0.17, 2.40 ± 0.15) in 6, 12, 24 μg/L T-2 toxin + 0.1 mg/L selenium groups were significantly higher than those in T-2 toxin groups (0.80 ± 0.08, 0.63 ± 0.08, 0.61 ± 0.11, t = - 12.259, - 11.279, - 13.371, P < 0.05). The expression levels of IGF-1R protein (1.67 ± 0.70, 1.07 ± 0.26) in 6, 12 μg/L T-2 toxin + 0.1 mg/L selenium groups were significantly higher than those in T-2 toxin groups (0.52 ± 0.05, 0.72 ± 0.05, t = - 25.977, - 10.776, P < 0.05). Compared with the control group [(5.33 ± 0.85)%, (4.03 ± 1.15)%], C28/I2 cells early apoptosis rates [(8.26 ± 1.51)%, (13.00 ± 0.72)%, (13.19 ± 1.05)%] in each of IGF-1R inhibitor groups, and late apoptosis rates [(8.50 ± 0.71)%, (14.21 ± 1.10)%] in 500, 1 000 μg/L IGF-1R inhibitor groups were increased significantly (P < 0.05). Conclusions The expressions of IGF-1R in the cartilage tissue of KBD children and T-2 toxin-poisoned rats under low selenium condition are decreased. T-2 toxin decreases the expression of IGF-1R in chondrocytes, and selenium can partly inhibit the effect of T-2 toxin on IGF-1R. Down-regulation of IGF-1R causes chondrocyte apoptosis, and it may play an important role in KBD chondrocyte apoptosis. Key words: Kaschin-Beck disease; Insulin-like growth factor-1 receptor; Chondrocytes; Cell apoptosis